A climograph packs a place's climate normals into one picture: average temperature for each month as a line, and average precipitation for each month as bars. With practice you can read a climate from it at a glance.
Key idea
From a climograph you can read the warmest and coldest months, the annual temperature range (warmest minus coldest), the total yearly precipitation (the sum of the bars) and when the wet and dry seasons come. If the warm months are December to February, the place is in the Southern Hemisphere.
Why it works
Each feature of the graph comes from a cause you have studied. A small annual range means the ocean or the tropics (why coasts stay mild); a large one means the middle of a continent at high latitude. A summer peak of rain means rising air in summer (the shifting tropical rain belt, monsoons or thunderstorms); a winter peak means storms on the westerlies in winter, as on the west coasts in the middle latitudes. The Southern Hemisphere's seasons are reversed because the Sun is high there from November to February.
Worked example: Reading Sydney
Sydney, Australia averages about 23.5 °C in January and 13 °C in July. What is its annual range, and what does the timing tell you?
- Range: $23.5 - 13 = 10.5$ °C, small, because Sydney is on the coast.
- January is the warm month, so Sydney is in the Southern Hemisphere.
Answer: 10.5 °C; Southern Hemisphere
Worked example: Wet season
A city's monthly precipitation (mm) from January to December is 0, 0, 0, 0, 15, 525, 840, 525, 340, 90, 15, 5. When is its wet season, and what is its yearly total?
- The rain is concentrated in June through September.
- Total: $15 + 525 + 840 + 525 + 340 + 90 + 15 + 5 = 2355$ mm.
- A wet summer and a long dry season: a monsoon climate like Mumbai's.
Answer: June–September; 2355 mm
Common mistake
Assuming the warmest months are always June to August. In the Southern Hemisphere they are December to February: Sydney, Cape Town and Buenos Aires have summer at Christmas. Check which months are warmest before naming the seasons.